Optical spectroscopic followup of AT2026nwl/EP260530a
ATel #17952; Christophe Adami (LAM/Pytheas/AMU), Stephane Basa (UAR Pytheas), Noemie Globus (UNAM), Alan M. Watson (UNAM)
on 9 Aug 2026; 14:31 UT
Credential Certification: Christophe Adami (christophe.adami@lam.fr)
Subjects: Optical, Transient
We report an optical spectroscopic followup of AT2026nwl/EP260530a. Originally
reported/characterized by Wu et al. (ATEL #17824), Wen et al.
(ATel #17825), Globus et al. (https://gcn.nasa.gov/circulars/44759), Zheng et al. (https://gcn.nasa.gov/circulars/44775), Guelfand et al.
(https://gcn.nasa.gov/circulars/44776), see also Junjie-Jin (https://gcn.nasa.gov/circulars/44782),
it was also spectroscopically characterized by Godson et al.
(https://www.wis-tns.org/object/2026nwl) on the 2026-05-31 with LT/SPRAT.
We observed it ourselves two times with the MISTRAL spectro-imager using the T193cm telescope
at Observatoire de Haute-Provence (France) on the 2026-06-02 (15min exposure time) and on the
2026-07-03 (30min exposure time).
MISTRAL spectrum of 2026-06-02 is very similar to the original spectrum of Godson et al., showing
HeI@7065A, Halpha@6563A, HeI@5876A, HBeta@4861A, HeII@4686A at z~0. HGamma@4340A however seems to
have disappeared between 2026-05-31 and 2026-06-02 (even if located in a low efficiency
spectral domain of MISTRAL).
MISTRAL spectrum of 2026-07-03 (roughly one month later) is different. The magnitude of the
object is significantly fainter, and while the continuum is still decreasing, nearly every signs
of emission line has disappeared. Only Halpha is remaining at a low S/N.
We acknowledge the excellent support from Observatoire de Haute-Provence and in particular
Jean Balcaen, Yoann Degot-Longhi Larralde Erasun, Stephane Favard, and Jean Pierre Troncin.
We also thank Jerome Schmitt and Jean Claude Brunel for the MISTRAl upgrade.
